Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain. Suprachoroidal implants were first investigated in Australia in the 1950s. In this approach, the neuromodulation hardware is positioned between the sclera and the choroid, thus providing significant surgical and safety benefits for patients, with the potential to maintain residual vision combined with the artificial input from the device. Here we review the latest advances and state of the art devices for suprachoroidal prostheses, highlight future technologies and discuss challenges and perspectives towards improved rehabilitation of vision.

The ability of assistive peripheral prosthetic vision to improve mobility performance in persons with constricted VFs has been demonstrated. In a prospective peripheral visual prosthesis, electrode array designs need to be carefully tailored to the scope of tasks in which a device aims to assist. We posit that maximum benefit might come from application alongside existing visual aids, to further raise life quality of persons living through the prolonged early stages of RP.

Simulated prosthetic vision (SPV) in normally sighted subjects is an established way of investigating the prospective efficacy of visual prosthesis designs in visually guided tasks such as mobility. To perform meaningful SPV mobility studies in computer-based environments, a credible representation of both the virtual scene to navigate and the experienced artificial vision has to be established. It is therefore prudent to make optimal use of existing hardware and software solutions when establishing a testing framework. The authors aimed at improving the realism and immersion of SPV by integrating state-of-the-art yet low-cost consumer technology. The feasibility of body motion tracking to control movement in photo-realistic virtual environments was evaluated in a pilot study. Five subjects were recruited and performed an obstacle avoidance and wayfinding task using either keyboard and mouse, gamepad or Kinect motion tracking. Walking speed and collisions were analyzed as basic measures for task performance. Kinect motion tracking resulted in lower performance as compared to classical input methods, yet results were more uniform across vision conditions. The chosen framework was successfully applied in a basic virtual task and is suited to realistically simulate real-world scenes under SPV in mobility research. Classical input peripherals remain a feasible and effective way of controlling the virtual movement. Motion tracking, despite its limitations and early state of implementation, is intuitive and can eliminate between-subject differences due to familiarity to established input methods.

Retinitis pigmentosa (RP) causes visual field (VF) constriction due to progressive loss of photoreceptors, typically from the retinal periphery to the fovea. Retinal prostheses offer vision restoration via electrode implantation and stimulation near the fovea, thereby eliciting articifial percepts, so-called phosphenes in the center VF. Although foveal photoreceptors can persist for prolonged periods of time, bionic therapy is usually restricted to stages of RP with complete vision loss. However, persons with RP experience mobility impairment from peripherally restricted VFs much earlier. Consequently, the amount of visual scanning necessary for navigation is increased, and maintaining a steady pace is challenging. Receiving a retinal implant at this early stage might be feasible. We investigated the potential of a peripheral visual prosthesis coexisting with central residual vision to facilitate scene perception and mobility. Simulating prosthetic and residual vision in a virtual mobility environment, we found that assistive phosphene layouts were associated with reductions in visual scanning-related head movements of up to 42.1%, body rotations of up to 30%, and up to 45% lower frequency of stopping when circumventing low-lying obstacles, pedestrians and following a path. Further research on early implantation of retinal prostheses for the peripheral VF is therefore advised.